1. Field of the Invention
This invention relates to an insert for an abrasive tool such as a drill.
2. Discussion of the Background
Composite abrasive compacts are products used extensively as inserts for abrasive tools such as drills. Such composite compacts comprise an abrasive compact layer bonded to a cemented carbide support. The abrasive compact will typically be a diamond abrasive compact, also known as polycrystalline diamond or PCD, or a cubic boron nitride compact, also known as polycrystalline CBN or PCBN.
The inserts are generally brazed into, or mounted in, a drill bit or similar tool and in so doing stresses may be introduced into the interface between the abrasive compact layer and the cemented carbide support. These stresses may be alleviated or reduced by providing a recess which extends into the cemented carbide support from the compact/carbide interface and which is filled with the abrasive compact.
Composite abrasive compacts are made under conditions of temperature and pressure at which the abrasive particle is crystallographically stable. They are generally produced in capsules, the outer dimensions of which are generally the same, or essentially the same, as the composite compact itself. Thus, a limited number only of such composite compacts may be produced in any one synthesis cycle.
EP 0 009 315 describes a method of making inserts suitable for tools or drill bits which includes the step of fragmenting a circular cylindrical or disc-shaped abrasive compact into a plurality of discrete, non-segmental fragments, the severing taking place along planes at an angle to the circular end-surfaces of the compact.
EP 0 223 474 describes a method of making a drill blank comprising a cylindrical carbide body having a vein of abrasive compact embedded in a groove at one end thereof, and bonded to the carbide. The method includes the steps of providing a solid, cylindrical body of cemented carbide having the end surfaces joined by a side surface, forming a series of grooves in one end surface, placing compact-forming material in the grooves, exposing the cylindrical body to temperature and pressure conditions suitable to produce an abrasive compact of the material in the grooves and severing the cylindrical body longitudinally from one end surface to the opposite end surface to produce a plurality of drill blanks.
EP 0 206 652 also describes a method of producing a plurality of drill blanks by severing a disc-shaped composite abrasive compact longitudinally.